1. Field of the Invention
The present invention relates to a packaging board, a semiconductor module, and a portable apparatus.
2. Description of the Related Art
A method for manufacturing a high-density printed circuit board with micropads, having a solder resist between soldering pads with narrow pitches has heretofore been disclosed.
FIG. 17 shows a sectional view of a conventional printed circuit board 500. Soldering pads 52 and a through hole pad 55 are formed on a copper-clad laminate board 51. A solder resist 53 is formed between the soldering pads 52 on the copper-clad laminate plate 51 so as to have openings over the soldering pads 52. A joint layer or solder coating 54 is formed on the soldering pads 52.
In this printed circuit board 500, the solder coating 54 has surfaces higher than the surface of the solder resist 53, and thus protrudes from the surface of the solder resist 53. Since the solder coating 54 protruding in this way impairs the flatness of the printed circuit board 500 at the surface, there has been the problem that the printed circuit board 500 lacks handleability in the steps of handling the printed circuit board 500 listed below.
(1) In the step of lifting the printed circuit board 500 by means of vacuum suction with the vacuum gripper (robot hand) of a vacuum conveyance system, the protrusions of the solder coating 54 create gaps between the suction port of the vacuum gripper and the surface of the printed circuit board 500, thereby hindering vacuum suction. This produces a conveyance error of the printed circuit board 500.
(2) In the step of clamping (fixing) the edges of the printed circuit board 500 with fixing members having a V-grooved structure, the fixing members may come into contact with protrusions of the solder coating 54 formed on the edges of the printed circuit board 500. The printed circuit board 500 can thus be fixed in a tilted state. Namely, it is prevented from being fixed in a proper position.
(3) In the step of packing the printed circuit board 500, the protrusions of the solder coating 54 make the packing unstable when a plurality of printed circuit boards 500 are stacked for package. This also causes an unnecessary increase in volume.
(4) In the step of attaching an auxiliary surface-protecting plate onto the surface of the printed circuit board 500, the protrusions of the solder coating 54 make it difficult to attach the auxiliary plate.
Moreover, in the steps (1) to (4), solder coating 54 coming into contact with other members can be scraped off or cause the adhesion of foreign objects, with a drop in connection reliability.